3GPP that is a standardization group of W-CDMA is studying a communication scheme that becomes a successor to W-CDMA (Wideband Code Division Multiple Access) and HSPA (High Speed Packet Access), that is, 3GPP is studying Evolved UTRA and UTRAN (another name: (LTE) (Long Term Evolution) or Super 3G). For example, OFDMA (Orthogonal Frequency Division Multiple Access) is adopted for downlink, and SC-FDMA (Single-carrier Frequency Division Multiple Access) is adopted for uplink.
OFDMA is a scheme for dividing a frequency band into a plurality of narrow frequency bands (subcarriers) so as to perform transmission by carrying data on each subcarrier. In OFDMA, by arranging the subcarriers on frequencies densely without interfering with each other while a part of them overlaps, high speed transmission is realized so that efficiency of use of frequency increases.
SC-FDMA is a single-carrier transmission scheme that can decrease interference among terminals by dividing frequency band and performing transmission using frequency bands that are different among a plurality of terminals. Since the SC-FDMA has characteristics that variation of transmission power becomes small, low power consumption in the terminal and wide coverage can be realized (refer to R. Dinis et al., “A Multiple Access Scheme for the Uplink of Broadband Wireless Access,” IEEE Globecom, December 2004, for example).
SC-FDMA used for uplink radio access in E-UTRA is described with reference to FIG. 1. The frequency band usable in the system is divided into a plurality of resource blocks. Each of the resource blocks includes one or more subcarriers. One or more resource blocks are assigned to the user apparatus (UE: User Equipment). In frequency scheduling, according to received signal quality or channel state information (CQI: Channel Quality Indicator) of each resource block in the uplink for each user apparatus measured by the base station apparatus, the base station apparatus assigns resource blocks preferentially to a user apparatus of a good channel state, so that transmission efficiency or throughput of the whole system can be improved. Also, frequency hopping may be applied for changing usable frequency blocks according to a predetermined frequency hopping pattern.
In FIG. 1, different hatchings indicate time/frequency resources assigned to different user apparatuses. UE2 assigned a wide band in a subframe is assigned a narrow band in a next subframe. Each user apparatus is assigned a different frequency band such that frequency bands do not overlap.
In SC-FDMA, each user apparatus in a cell performs transmission using different time/frequency resources. Accordingly, orthogonality among user apparatuses in the cell can be realized. In SC-FDMA, by assigning continuous frequency, single-carrier transmission of low PAPR (Peak-to-Average Power ratio) can be realized. Therefore, coverage area can be increased in the uplink in which there is strict limitation for transmission power. In SC-FDMA, a scheduler of the base station apparatus determines the time/frequency resources to be assigned based on propagation status of each user and QoS (Quality of Service) of data to be transmitted. QoS includes data rate, required error rate and delay. Accordingly, by assigning time/frequency resources of good propagation status to each user, throughput can be increased.